Nine patients with anorexia nervosa were studied by echocardiography, ECG, maximal treadmill exercise testing and 24 hr taped ECG; 3 underwent Tc99m radionuclide angiography at rest and exercise. Although cardiac performance was unimpaired, 3/4 patients in whom left ventricular mass was below 95% predictive limits had ventricular ectopy. No patient with heart size appropriate for body surface area evidenced ectopy. Repeat echocardiograms in 6/9 patients performed after mean 27% weight gain showed 28% increase in LV mass and 21% increase in left atrial dimension. Cardiac size may increase following weight gain in Anorexia Nervosa. Ventricular ectopy may be present despite normal LV mechanical function.